If you have a current subscription as a Premium Member, you do not need to purchase these classes, they are included with your membership. You can access them in the Studio and in the Community. Currently, there are over 100 classes in the Studio located here.
Otherwise, when your complete your purchase of any class below (updated on a regular basis), you will have a downloadable file containing instructions on accessing the class. You can also click here to become a premium member for access to all classes.